Global concerns over depleting supplies of fossil fuel and global warming have resulted in extensive research in area of renewable energy. Energy storage plays a vital role in conversion of energy obtained from renewable resources to energy grid.
One such energy storage system is rechargeable batteries, which play a vital role in daily utilities like computers, mobile phones, and electric vehicles (EVs). Existing rechargeable battery systems include lead-acid, nickel-cadmium, nickel-metal hydride (Ni-MH), and lithium-ion batteries (LIBs). Most of these systems have intrinsic problems. For example, lead acid and nickel cadmium systems suffer from low energy density, and environmental concerns stemming from use of toxic materials such as lead and cadmium, while Ni-MH batteries have issues with large self-discharge.
LIBs face high safety risks due to flammability of organic electrolyte and reactivity of the electrode material with the organic electrolyte during overcharging or short-circuiting. Consequently, manufacturing of LIBs requires sophisticated cell assembly technologies involving a dry and air-tight environment to prevent premature oxidation/hydroxylation of lithium ions. Such demanding processing conditions lead to high product costs of LIBs. Moreover, large-scale energy storage technologies translate into considerable concern regarding safety and toxicity, alongside electrochemical issues related to loss of energy density and efficiency. Most of the major fires and accidents in automobile and aircraft engines are related to lithium ion batteries.
In view of the above, there is a need for development of low-cost, safe, high-power alternatives to conventional LIBs for use in large scale applications such as electric vehicles.
A possibility for energy storage in the form of aqueous rechargeable lithium ion battery (ARLB) has been developed. This is a safer alternative and may be competent enough to match performance of current LIBs. One major advantage of ARLB systems relate to use of water as the electrolyte medium. For example, a leakage in an ARLB package is unlikely to result in fire and/or to reduce performance of the battery. This renders ARLB technology useful for many applications such as electric vehicles, large scale grid based energy storage, and in portable and wearable electronics.
Notwithstanding the above, presence of complicated reactions in a typical ARLB means that selection of electrode materials in ARLB remains challenging. For example, electrode materials that do not release oxygen or hydrogen during battery charge-discharge process are needed to allow use of ARLB in practical applications. This specific requirement translates into limitations in terms of the overall voltage and therefore, energy density of the battery. Therefore, design of new electrode materials for ARLBs with enhanced performance is of great importance.
In view of the above, there remains a need for an improved material for use in electrochemical cells, in particular aqueous rechargeable batteries, that overcomes or at least alleviates one or more of the above-mentioned problems.